The current invention is directed to an apparatus for providing an adjustable support for an object, such as that used to support visual monitors or computer keyboards.
Certain objects, such as data entry keyboards for use in connection with a computer and visual monitors, have been mounted on a support surface formed on an adjustable support apparatus that permits varying the height, as well as the inclination, of the support surface. Varying the height and inclination of the object reduces strain on the user. For example, varying the height and inclination of a keyboard permits its positioning to be adapted to the characteristics and preferences of the user and can prevent carpel tunnel syndrome.
In the past, apparatus for supporting keyboards have included an arm, the proximal end of which was rotatably mounted on a base that was typically affixed to the underside of a desk. A support plate, on which the keyboard is mounted, is rotatably mounted on the distal end of the arm. Rotating the arm up or down at the base allows the height of the keyboard to be adjusted, while rotation of the support plate on the arm allows the inclination of the keyboard to be adjusted. A device, such as a torsion spring, is typically used to offset the weight moment tending to rotate the support arm downward when it is unlocked. Another approach to offsetting the weight moment involves the use of a gas filled cylinder, similar to those used to restrain downward motion of the tailgate or hatch back in an automobile. Still another device makes use of a constant force spring, such as that disclosed in U.S. Pat. No. 6,227,508 (application Ser. No. 09/248,403, filed Feb. 12, 1999), hereby incorporated by reference in its entirety.
Various locking mechanisms have been used to lock the support arm and support plate in the desired orientations. Some devices employ two or more knobs or levers to effect complete locking or unlockingxe2x80x94for example, one knob to lock/unlock the support arm and another to lock/unlock the support plate. Consequently, adjustment of the apparatus is cumbersome. In addition, the inclination of the support plate varies as the arm is rotated up and down, whereas the user will often desire to maintain a constant horizontal inclination for the keyboard regardless of its height. Consequently, in many prior art devices, resetting the height of the keyboard will also necessitate resetting the inclination.
Aforementioned U.S. Pat. No. 6,227,508 discloses an apparatus that allows the user to maintain constant inclination of the support plate as the support arm rotates and that employs ratchet and pawls to lock rotation of the support arm and the support plate. Unfortunately, the ratchet and pawl mechanism for locking the support arm does not give a smooth feel to the user and can create unacceptable noise in an office environment. Also, the ratchet and pawl limits the support arm height adjustment to incremental movement.
Consequently, it would be desirable to provide an improved adjustable support apparatus for an object, such as a keyboard or a visual monitor.
It is an object of the current invention to provide an improved adjustable support apparatus for an object, such as a keyboard or a visual monitor. This and other objects is accomplished in an adjustable support apparatus for supporting an object thereon that can be adjusted by a user that comprises (a) a base; (b) a rotatable support arm capable of rotation relative to the base over at least a range of angular orientations, the support arm having first and second ends, the support arm comprising a first link having first and second ends, the first end of the first link coupled to the base at a first location so as to be capable of rotation about the base and so as to be capable of displacement relative to the base; (c) a support member for supporting the object, the support member coupled to the second end of the support arm; (d) an engageable and disengageable mechanism for locking rotation of the support arm about the base in at least a first direction, comprising: (i) first and second contact members formed on one of the base or the first end of the first link, the first and second contact members spaced apart by a distance and defining a line extending therethrough, (ii) at least a segment of a ring formed on the other of the base or the first end of the first link, the ring segment having inner and outer arcuate surfaces, the ring segment having a radius of curvature that defines a center thereof, the ring segment disposed between the first and second contact members, wherein, when the center of the ring segment radius of curvature is displaced a first distance from the line extending through the first and second contact members, application of a load on the support member causes the first contact member to impart a force on the ring segment inner surface and causes the second contact member to impart a force on the ring segment outer surface, the forces generating a friction force that restrains rotation of the first link in the first direction, whereby the locking mechanism is engaged and the support arm is restrained from rotation in the first direction, and wherein, when the first link and the base undergo relative displacement so that the center of the ring segment radius of curvature is displaced a second distance from the line that is less than the first distance, application of a load on the support member does not cause the first and second contact members to exert forces on the ring segment inner and outer surfaces, respectively, that generate friction forces that restrain rotation of the first link in the first direction, whereby the locking mechanism is disengaged and the support arm can be rotated in the first direction.
The current invention also encompasses a method of engaging and disengaging a locking mechanism in a support apparatus for supporting an object thereon that can be adjusted by a user. The support apparatus comprises: (i) a base, (ii) a rotatable support arm capable of rotation relative to the base over at least a range of angular orientations, the support arm having first and second ends, the first end of the support arm coupled to the base so as to be capable of rotation about the base, at least a portion of the support arm coupled to the base so as to be capable of translation relative to the base, (iii) a support member for supporting the object, the support member coupled to the second end of the support arm, and (iv) an engageable and disengageable mechanism for locking downward rotation of the support arm about the base comprising (A) first and second contact members projecting from one of the base or the translatable portion of the support arm, the first and second contact members spaced apart by a distance, and (B) at least a segment of a ring formed on the other of the base or the translatable portion of the support arm, the ring segment having inner and outer arcuate surfaces and disposed between the first and second contact members. The method of engaging and disengaging the locking mechanism so as to restrain downward rotation of the support arm about the base comprises: (a) engaging the locking mechanism by translating the translatable portion of the support arm in a first direction so as to cause the first contact member to contact the inner surface of the ring segment and the second contact member to contact the outer surface of the ring segment; and (b) disengaging the locking mechanism by translating the translatable portion of the support arm in a second direction opposite from the first direction.